High-strength wire rope



United States Patent 3,259,487 I HGH-STRENGTH WIRE ROPE Howard E. Mueller, Shaker Heights, Richard A. Nickola, Bedford Heights, and Gordon T. Spare, Chardon, ()hio, assignors to United States Steel Corporation, a corporation of Delaware Filed Jan. 31, 1963, Ser. No. 255,411 8 Claims. (Cl. 75-123) This invention relates to improvements in the manufacture of high-strength wire rope.

The manufacture of high-strength rope or cable requires the use of heavily cold drawn, relatively highcarbon steel wire; e.g., cold drawn AISI grade C-1060 (carbon 0.55/0.65; manganese 0.60/0.90; silicon 0.10/ 0.30; phosphorus 0.04 maximum; sulphur 0.05 maximum), is commonly used for this purpose. Cold drawing to effect a reduction in cross-sectional area of at least 60% is essential to develop the desired structure and strength level in the steel. Such cold drawing results in an undesired decrease in ductility and in rendering the steel age-hardenable. Since the rate of age hardening varies directly with temperature and since considerable heat is generated in the drawing operation, a portion of the ductility loss noted immediately after drawing may be attributable directly to this phenomenon; in any event, additional loss due to aging subsequent to drawing can render the wire unsuitable for stranding and laying into rope.

The aging phenomenon has been attributed to the presence of nitrogen in the steel. It is known, for example, that aging is substantially eliminated in fully deoxidized low carbon steels to 'whichaluminum has been added in excess of the amount required for full combination with the nitrogen present; also that aging effects in steels are diminished by special steelmaking practices, e.g., vacuum casting, which reduce the nitrogen content to abnormally low levels. Both these expedients, however, add considerably to steelmaking and processing costs.

Accordingly, it is an object of the present invention to control aging in the manufacture of wire rope without resort to either of the aforementioned expedients.

The achievement of this and other objects will be set forth in the following specification which is to be read in conjunction with the attached drawing wherein:

FIGURE 1 is a graph showing the effect of age hardening at 500 F. for various time intervals on the torsion ductility of a series of 0.60 carbon steels cold drawn from inch diameter rod to 0.095 inch diameter wire in accordance with normal wire drawing practices, and

FIGURE 2 is a similar graph but relating to a series of 0.60 carbon steels in which the nitrogen content has been adjusted to abnormally high and abnormally low levels.

The torsion ductility test is used to determine the suitability of wire for the manufacture of rope and cable. The test comprises clamping a specimen of the wire between a fixed and a rotatable chuck spaced apart to expose a gage length of the wire equal to 100 times the wire diameter, and then twisting the specimen to failure. Experience has shown that, for use in high quality, highstrength cable, the wire must withstand a twist T: [29.5-(d)] in a length, ll00 d, where d is the diameter of the wire; thus in the case of 0.095 inch diameter wire, the minimum acceptable torsion test value is T =27.l.

With particular reference to FIGURE 1, Curve A is typical of wire drawn from the A181 C-l060 steels; Curve B shows the effect of decreasing the nitrogen content of such steels; Curve C, the effect of addition of sutficient aluminum to combine with the nitrogen nor- 3,259,487. Patented July 5, 1966 mally present in this grade; while Curve D is peculiar to a steel containing less than about 0.015% silicon but otherwise conforming to the C-l060 analysis.

Analyses of the four steels referred to above as well as the analyses of steels to be discussed in connection with FIGURE 2 are tabulated below:

Steel 0 Mn Si Al N 0. 61 0. 77 0. 24 0. 06 0. 006 0. 58 0. 83 0. 27 nil 0. 002 0. 61 0. 76 0. 24 0. 18 0. 005 0.59 0. 71 0. 015 0. 06 0. 006 0. 56 0. 79 0. 26 0. 120 0. 002 O. 57 0. 81 0. 26 0. 160 0. 012 0. 54 0.81 0. 015 nil 0. 002 O. 58 O. 85 0. 015 nil 0. 012 0. 58 0.83 0. 26 nil 0. 012 0. 58 0.81 0. 015 0. 120 0. 002 0. 59 0. 87 0. 0. 0. 010 0. 59 0. 73 0. 015 0. 0. 006

All of the above contained 0.04 maximum phosphorus and 0.05 maximum sulphur; the balance, iron plus the usual residuals of other elements.

As shown by Curve A, cold drawn C-1060 steels age quite rapidly; as little as six seconds at 500 F. being sufficient to reduce the torsion ductility below acceptable standards. The rate of aging is slowed by vacuum casting such steel to reduce the nitrogen content thereof but the improvement efi'ected, indicated by Curve B, would not justify the cost of this treatment in wire manufacture. As might be expected and as shown by Curve C, the addition of sufiicient aluminum affords a marked improvement and maintains acceptable ductility values even after extended time at temperature which accelerate the aging. More remarkable, however, is the effect of decreasing silicon below about 015%; this, as indicated by Curve D, affords essentially the same result as the addition of an excess of aluminum. It will be noted that the torsion ductility value T remains above 30, even after aging 1 /2 hours at 500 F.

Insofar as we are aware, this silicon effect has not been observed before and is not readily explainable. The fact that the improvement in torsion ductility is occasioned on one hand by a decrease in silicon and on the other by an increase in aluminum, is an indication of a difference in mechanism. This is further evidenced by the fact that the aluminum addition is equally effective in steels containing both abnormally high and abnormally low nitrogen (compare Curves E and F of FIGURE 2 and C of FIGURE 1),; whereas; decreasing the silicon trogen is normal (see Curves A and D of FIGURE 1) or abnormally high (see Curves H and K of FIGURE 2), has a detrimental effect when the steel is abnormally low in nitrogen (compare Curve G of FIGURE'Z with B of FIGURE 1). However, decreasing the silicon content of the high aluminum-steels C, E and F to less than 0.015%, as in steels'E', F and C, makes no significant change in the torsion ductility behavior. The curves for steels E, F and C have not been plotted since they fall substantially atop curves E, F and C. The latter indicates the individual silicon and aluminum effects to be non-additive which is indicative of the same mechanism of operation.

However, although we cannot presently offer an .explanation of the mechanism, our discoveries concerning the effect of decreasing silicon to below 0.015% on the torsion ductility of high carbon steels affords a cheap and reliable way of eliminating the aging difiiculties associated with use of these steels in the manufacture of highstrength wire. The benefits are attained by deletion of the re-siliconization step in the steelmaking operations.

content, while remarkably effective when ni- The latter are otherwise conventional and utilize iron and scrap of normally available composition to produce steels characterized by a normal nitrogen content, i.e. nitrogen ranging from about 0.004 to 0.008%. In practice, we prefer to aim to melt to 0.01% silicon, re-carburizing and adjusting manganese as may be needed to provide carbon 0.55 to 0.65%, manganese 0.60 to 0.90 in the finished steel. The phosphorous and sulphur eliminations should be regulated to reduce these impurities to a maximum of at least 0.04 and.0.05% respectively, and preferably to about 0.015% phosphorus and 0.020% sulphur. Aluminum is used only to the extent normally required by good ingot practice. Limiting the use of aluminum to the latter purpose, limits the function of aluminum to deoxidation and the aluminum content of the steel to a maximum of about 0.07% as compared to the 0.10 to 0.20% of this element required if nitrogen is to be combined. The present invention makes the use of such excess aluminum unnecessary and avoids the costs and difficulties associated therewith. The steel is hot worked into rod, treated, cleaned and cold drawn into wire in accordance with conventional practices. If the wire is subjected to an intermediate patenting; the drawing schedule is arranged so that the drafting subsequent to such patenting will cold work the wire to the degree required to impart the desired tensile strength thereto. To develop tensile strength in excess of 220,000 p.s.i. as required for high strength rope, the final drafting must effect a reduction in area of between 75 and about 90%. Any of conventional practice for stranding and laying a plurality of cold drawn wires into rope or cable may be used. As noted in the discussion of FIGURE 1, the present invention provides wire characterized by a torsion ductility value, T, of 30 or greater even after extending aging. In this respect, the wire significantly exceeds standard requirements as determined by the formula T=29.525 (d). This improvement in combination with tensile strength in excess of 220,000 p.s.i. are readily achieved in 0.60 carbon steel wire. The rope manufactured therefrom is therefore of exceptional quality, service life and useful strength.

Although the invention has been described in relation to the 0.60% carbon steels most commonly used in highstrength wire rope and cable, it is also applicable in the manufacture of such products from higher carbon steels. In general, aging tendencies are diminished and an improvement in torsion ductility obtained by limiting silicon to 0.015 maximum in any cold drawn wire within the following composition range: carbon, 0.55/0.85; manganese, 0.35/ 1.20; phosphorus, 0.04 maximum; sulphur, 0.05 maximum; nitrogen, 0.004/0.0l2; balance iron and normal residuals. As indicated above the aluminum content preferably should not exceed about .07% to obtain the full benefits of the invention.

While we have described certain specific embodiments of our invention, it is apparent that modifications may arise. Therefore, we do not wish to be limited to the disclosure set forth but only by the scope of the following claims.

We claim:

1. In high-strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising heavily cold drawing said wires from steel consisting essentially of Percent Carbon .55/.85 Manganese .35/1.20 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.012 Silicon .015 max.

balance iron and other elements in residual amounts, said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

2. In high-strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising heavily cold drawing said wires from steel consisting essentially of Percent Carbon .55/.85 Manganese .35/ L20 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.012 Silicon .015 max. Aluminum .07 max.

balance iron and other elements in residual amounts, said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

3. In high-strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising heavily cold drawing said wires from steel consisting essentially of Percent Carbon .55/.65 Manganese .60/ .90 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.0l2 Silicon .015 max.

balance iron and other elements in residual amounts, said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

4. In high-strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising heavily cold drawing said wires from balance iron and other elements in residual amounts, said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

5. In high strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising forming said wires from steel consisting essentially of Percent Carbon .55/.85 Manganese .35/l.20 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.0l2 Silicon .015 max.

Percent Carbon .55/.85 Manganese .35/l.20 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.0l2 Silicon .015 max.

Aluminum .07 max.

Percent Carbon .55/.65 Manganese .60/ .90 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/.012 Silicon .015 max.

balance iron and other elements in residual amounts and cold drawing said wires to effect a reduction in area of between 75 and 90%, said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

8. In high strength steel rope and cable comprising a plurality of cold drawn stranded steel wires, the improvement comprising forming said wires from steel consisting essentially of Percent Carbon .55/.65 Manganese .60/.90 Phosphorus .04 max. Sulphur .05 max. Nitrogen .004/ .012 Silicon .015 max. Aluminum .07 max.

balance iron and other elements in residual amounts and cold drawing said wires to eifect a reduction in area of between and said cold drawn wires having a tensile strength in excess of 220,000 p.s.i.

References Cited by the Examiner Aluminum in Iron and Steel, page 193, edited by Case et al., published in 1953 by John Wiley and Sons, New York.

DAVID L. RECK, Primary Examiner. 

2. IN HIGH-STRENGTH STEEL ROPE AND CABLE COMPRISING A PLURALITY OF COLD DRAWN STRANDED STEEL WIRES, THE IMPROVEMENT COMPRISINGG HEAVILY COLD DRAWING SAID WIRES FROM STEEL CONSISTING ESSENTIALLY OF 